Multiple lay cable



Jul 25,1933. J, GRQBL 1,919,509

MULTIPLE LAY CABLE Filed Aug. 24, 1929 I056; INVENTOR;

x4, Attarney.

scribed with reference to Patented July 1933 UNITED STATES PATENT OFFICE J'OSEF GBbBL, OF SOLLN NEAR MUNICH, GERMANY, ASSIGNOB TO THE PM BAYER-NWEBK AKTIENGESELLSCHAIT, 0F GERIANY MULTIPLE LAY CABLE Application filedhugust 24, 1929, Serial No.

In the installation of cables, particularly of long-distance lines, cracking of the cables is often experienced though the specific load amounts to not more than about of the breaking resistance determined in the lab oratory tests. Researches have shown that these breaks are caused by the specific form of the cables. Cables are formed by helically disposed wires. These helically wound wires give rise to transverse forces, exerting torsional moments-proportional to the length of their lever arms. As the directions of the lays (winding directions) are alternating, the resulting differential torsional moment will twist the cable and thereby disturb the equal specific distribution of the load. Therefore it is desirable to prevent the occurrence of those differential torsional moments, i. e. to make the difference equal to zero.

In the following, my invention will be dethe accompanying drawing, in which Figure 1 is a transverse sectional view of a three-lay cable with alternating winding direction, and i Figure 2 is a transverse sectional View of a I three-lay cable, the two innerlays thereof be- 11 and 14),

mg turned to the left, while the is turned to the right.

The resent invention solves the problem of'elimmating torsional moments by disposing the layers on a core in such a way that in the outermost layer the pitch of the individual wires is ater than that of the wires of the inner ayer, whereby the diam eter of the individual wires of the outer layer is smaller than that of the individual wires of the inner layer. It has been found that the dimensions of the wires and their pitch several layers have a certain inter-reoutermost lay in the lationship and ,the theroretical tests made have shown that freedom from torsion may be obtained by causing the cable to meet the condition wherein each of the above terms refers to a single layer and D is the mean diameter of the lay, Z is the number of elements of the lay, c is the factor of turn lengths (between 8 is the diameter 0 one element,

and to base the 388,138, and in Germany September 8, 1928.

v is comparable to the pitch of a screw thread.

The turn length factor is defined as the factor by which the diameter (D) of a layer is to be multiplied to get the pitch, i. e. the length of a turn measured parallel to the cable axis. The preferable extreme values to be used are 11 and 14.

In practice it is preferable to eliminate the quantities l) and Z from the equation equation exclusively on the quantities 8 and e.

For a three-lay cable with alternating Winding directions and 8 =8 the theoretical derivation furnishes the following condition f 11 02) '00 73 wherein (3) is 31. The diameters 8 of the core wire,

8 of a wire of the lay 1, and 8, of a wire of the lay 2 are of equal size. The diameter 3 of a wire of lay 3 is about With respect to the total cable diameter A there is Within the turn length =11-14 the determination of other diameters and numbers of wires are possible, their appiication however, is less practica For a three-lay cable with two parallel inner lays for instance to the-left) and one outer lay disposed in the opposite direction, the condition for freedom from torsion is In this case is to be inserted as minimum, likewise as minimum, a; as maximum. The constants a, b, c, d and e remain the same as in the preceding example. Figure 2 shows in cross section a three-lay cable of this kind. The inner lays 1 and 2 of this cable are turned to the left and the exterior lay 3 is turned to the right. Differing from the preceding example in this case Z (number of wires of the exterior lay 3) is 25. v

In this way the equations for four and more lay cables may be determined.

What I claim is:

1. A three or more strand cable comprising a core, a plurality of layers wound thereupon, each layer comprising a plurality of ,individual elements, the diameter of each of the individual elements of the inner layers being greater than that of the individual elements of the outermost layer and the pitch of the individual elements of the inner layers being smaller than that of the individual elements of the outermost layer, whereby the dimensions of the said cable constituents and the pitch are correlated and defined by the following equation:

layer, designates the factor by which the diameter of a layer, measured from outer circumference to outer circumference, must be multiplied to obtain the length of one turnover of the layer measured parallel to the longitudinal axis of the cable, 8 designates the diameter of an individual element of a layer, the plus marks and minus marks indi- Cate the left and ri ht winding direction respectively, and the indices 1, 2 n indicate the layer member counted from the core of the cable.

2. A three strand cable comprising a core, three layers wound thereupon and each layer comprising a plurality of individual elements, the two inner layers having the same winding direction, the outermost layer having a winding inverse to that of the inner layers, said inner layers moreover having the smallest possible pitch and the outermost layer having the greatest possible pitch, whereby the dimensions of the said cable constituents and the pitch are correlated and defined by the following equation:

2 a s a T T I in which D designates the diameter of a layer from mid portion to mid portion, Z designates the number of the individual elements of a layer, 6 designates the factor by which the diameter of a layer, measured from outer circumference to outer circumference, must be multiplied to obtain the length of one turnover of the layer measured parallel to the longitudinal axis of the cable, 8 designates the diameter of an individual element of a layer, the plus and minus marks indicate the left and right winding direction respectively, and the indices 1, 2 and 3 indicate the first, second and third layer counted from the core.

J OSEF GROBL. 

